Self-test Questions:

Which of these cells are primitive cells?

How many lattice points per cell?

Can you see any n-fold rotation axes, where
n =

3

4

2

(Look for them by rotating the object until an n-fold axis
is perpendicular to the screen: do you see the n-fold symmetry
now?)
How many rotation axes are there of each type? What are their Miller
indices?

How about mirror planes?

View each of the cubic cells along a <111> direction. What is
the rotational symmetry about this axis? Which structure (sc, fcc,
bcc) is the most/least densely packed?